This invention relates to encoding of a moving picture signal and, more particularly, to a method of controlling the encoding and to an encoding device for encoding the moving picture signal with control of the encoding.
A method and a device for controlling encoding of an input moving picture signal into an encoded picture signal are disclosed in a prior U.S. patent application Ser. No. 187,380 which was filed Apr. 28, 1988 now U.S. Pat. No. 4,887,156, by Junichi Ohki, the present inventor, and is incorporated by reference in the instant specification. According to the prior patent application, the input moving picture signal is used in deciding a ratio which a moving picture area has relative to a frame picture represented by each frame of the input moving picture signal. More specifically, a frame memory is used to memorize the input moving picture signal as a memorized moving picture signal frame by frame. The input and the memorized moving picture signals are used in deciding the ratio.
The ratio is used in controlling a bit rate at which the encoded picture signal is produced. More in detail, the input moving picture signal is transformed into transform coefficients having frequencies variable between a zero frequency, namely, a DC component, and a high frequency. The ratio is used in limiting the transform coefficients to lower frequency ones when it is necessary to keep the bit rate below a certain bit rate.
It was confirmed that the control was well performed according to the prior patent application with a high encoding efficiency and with a reproduced moving picture which was agreeable to watch. The fact should, however, be noted that the transform coefficients of higher frequency components are suppressed or omitted when band limitation is necessary.